84 THE CRITERIA OF LIVINGNESS 



building, winding-up processes are summed up in the term 

 anabolism; the disruptive, analytic, down-breaking, running- 

 down processes are summed up in the term katabolism, both 

 sets of processes being included in the term metabolism, for 

 which we have, unfortunately, no English equivalent like 

 the German word ' Stoffwechsel ', change of stuff. But when 

 Verworn says " The life-process consists in the metabolism 

 of proteids ", he, like Huxley, is summing up too simply ; 

 it would be more correct to say that living always involves 

 the metabolism of proteids or proteins. 



(b) Specificity or Individuality of Metabolism. 



A second feature is that each organism has its chemical 

 individuality, and associated with this a specific structural 

 collocation. There is a chemical specificity in the milk of 

 nearly related mammals, and in the grape-juice of nearly 

 related vines. A stain due to the blood of a rabbit can 

 be readily distinguished from a stain due to the blood of 

 a man a fact that has been used with effect in some modern 

 murder trials. Nay more, the blood of a horse can be 

 distinguished from that of an ass. The crystals of the red 

 blood pigment of a dog differ from those of a wolf; indeed, 

 those of a domestic dog differ from those of the wild or 

 feral Australian dingo. The familiar fact that there are 

 individuals who cannot eat particular kinds of food, such 

 as eggs, or oysters, without more or less serious symptoms 

 is another illustration of specificity which is actually indi- 

 vidual. It looks as if a man were individual not merely 

 as to his finger-prints, but as to his chemical molecules. Even 

 the sexes differ in their metabolism, as is diagrammatically 

 shown in one or two cases where the colour of the blood 

 is actually different. We are here in contact again with 



